Ten cruises and it has always taken 1.5-2 hours for us whether we have been seated with others or just our family. It's not because the service is slow at all. Going to dinner in the MDR isn't like sitting down at your local diner, it is more of an experience. We get there close to the start time so that our servers can start the process. You are greeted, given the menus, drink orders are taken, recommendations are given, order taken, bread and drinks brought out, appetizers, soup/salad, entrée, desert menu presented, order taken, desert. The table is prepped for each course, which isn't a drawn out process and your server will be plating your table as you progress taking care of this as the meal progresses. They clear the crumbs after the entrée before desert.
Each course is prepped in the kitchen at the same time so if you skip the app and salad you won't be starting with your entrée right away. Last cruise we were amazed at our server. It had to have helped that we knew what we wanted fairly quickly, but he had our order in before most of the other teams around us because we always were the first tables to get our food that we could see. We never felt rushed at all. For us, there is a lot of food so we enjoy taking our time during dinner. During the meal your servers will be coming by, interacting, then your head server should also come by. Fitz was our head server last cruise and we saw him at least twice each night during dinner, not counting when we were entering/exiting the MDR. Our previous cruise we were not in his section but he still came by to check on us each night since we have known him since 2006.
You only get the menu the night before to preorder if you have a dietary issue such as a food allergy. You can review the menus here online before your cruise.